Method for forming structure suitable for use as a core member

ABSTRACT

Core-type structures are formed by extruding elongated tubular members or sheets of a thermoplastic material that are subsequently cut into segments or plates having a defined length and then assembled into a bundle. The bundle is then simultaneously cut at a number of spaced-apart locations along the length of the bundled segments, or plates, whereby a plurality of separate core structures are simultaneously formed.

This is a division, of application Ser. No. 09/024,173, filed Feb. 17,1998.

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates generally to a method for forming a structuresuitable for use as a core member, either by itself or as part of amulti-ply panel, and more particularly to a method for forming such astructure having a plurality of elongated passageways disposed parallelto the thickness of the core structure.

2. History of Related Art

Many structural arrangements have been proposed for use as a core memberin laminated assemblies such as multi-ply panels having a surface plybonded to at least one side of the core member. In particular, corestructures formed of short elongated tubular segments arranged inparallel to the thickness of the core member have been found to provideexceptional resistance to compressive deformation and crush damage.However, because such structures comprise very large numbers of separatetubes or similar cell components, they have heretofore been difficult toassemble and manufacture economically. For example, U.S. Pat. No.5,032,208, issued Jul. 16, 1991 to Horst Strauss describes a process formanufacturing a bundle of tubes by loading the tubes into a gutterhaving a moveable end wall. The end wall is then moved incrementally toexpose one end of the tubes, which are then cut and the cut ends fusedwhereby adjacently disposed tube ends are joined together. The bundle isthen moved to a position whereat a second cut can be made, then moved toa position at which a third cut can be made, and continued, seriatim,until the entire bundle has been cut into the desired number of cores.The Strauss process is not only cumbersome, allowing only one transversecut and fusing operation at a time, but also is dependent upon precise,controlled movement of one end of the gutter while maintaining a desiredalignment of the uncut tubes in the bundle.

In an earlier arrangement, a structural core panel construction isdescribed in U.S. Pat. No. 2,477,852, issued Aug. 2, 1949 to C. E.Bacon, in which short tubular members are adhesively joined along theirentire length. Alternatively, other shapes, such as corrugated stripsmay be precisely aligned and adhesively joined together along matingcorrugations and then transversely cut to provide a core. In all of thearrangements taught in the Bacon structure, the individual componentsare adhesively joined along their entire length. This process is alsocumbersome and time consuming, requiring that the adhesive be set beforemoving the structure for subsequent processing, such as applying a coverto the core member.

Recently, U.S. Pat. No. 5,683,782 issued Nov. 4, 1997 to Rainer Duchenedescribes a process for producing a honeycomb structure in which theindividual components of the structure are coated with a heat-activatedadhesive prior to assembly. After assembly, the adhesive is activated bya thermal treatment in which the individual components are bonded alongtheir entire length. Thus, the Duchene process requires a precoatingstep prior to assembly and a separate thermal treatment prior tosubsequent processing.

The present invention is directed to overcoming the problems set forthabove. It is desirable to have a method for forming a structure suitablefor use as a core in which a plurality of cores may be formed bysimultaneous multiple cuts of a pre-assembled stack, or bundle, ofcomponents having internal passageways. It is also desirable to havesuch a structure that does not require adhesive joining of the separatecomponents prior to forming into a core member. Furthermore, it isdesirable to have a method by which a structure suitable for use as acore member can be formed without requiring a fixture having a moveableend wall by which only a single core member is formed before requiringmovement of the assembled tubes to a subsequent position at whichanother core may be formed. Moreover, it is desirable to have a methodfor forming a plurality of cores simultaneously by which only selectedopen ends of the elongated members forming the core are fused together.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, a method offorming a structure suitable for use as a core member includes extrudinga thermoplastic material into an elongated tubular shape, cutting theelongated tubular shape into a plurality of separate segments, and thenaligning the separate segments in side-by-side relationship along theirlengths. The aligned segments are then formed into a row having apreselected width, after which the rows are assembled one on top ofanother to form a stack of the rows. Thus the stack has a widthsubstantially equal to the width of the rows of aligned segments, adepth substantially equal to the length of the segments, in the rows,and a height determined by the number of rows of aligned segmentsassembled in the stack. The stack of assembled rows is then cut in adirection transverse to the longitudinal axes of the aligned segments ata plurality of preselected spaced-apart distances, forming a pluralityof separate cores each of which has a width and height substantiallyequal to the width and height of the stack and a thickness determined bythe preselected distance between the transverse cuts. Simultaneouslywith cutting the stack of assembled rows, the aligned segments are fusedto each other at at least one of the respective cut ends of thesegments.

In other aspects of the present invention, the elongated tubular shapemay have a hollow circular cross section, a hollow rectangularcross-section, a hollow triangular cross-section, a hollow hexagonalcross-section, or may have at least one transversely disposed internalwall forming a plurality of separate elongated hollow cells extendingalong the length of each of the tubular shapes. Other features of themethod for forming a structure, in accordance with the presentinvention, include in the aligning step also moving the segments along aguideway having sidewalls that converge to a spaced-apart distancesubstantially equal to the length of the segments, and agitating atleast one of the segments or the guideway during movement of thesegments along the guideway. Other features of the method of forming arow of aligned segments also include fusing at least one of the cut endsof each of the aligned segments to the cut end of at least oneadjacently disposed segment. The fusing of the cut ends may includeheating the ends to a temperature sufficient to at least partially meltthe cut ends of the aligned segments or mechanically bonding at leastone of the cut ends of the aligned segments to the cut end of at leastone adjacently disposed segment.

Yet another feature of the method of forming a structure, in accordancewith the present invention, includes cutting the stack of assembled rowsof aligned segments by making a plurality of simultaneous transversecuts at spaced-apart distances along the longitudinal axes of thesegments.

In accordance with another aspect of the present invention, the methodof forming a structure suitable for use as a core member includesextruding a continuous thermoplastic sheet having a predefined width, atleast one surface extending across the width of the sheet, and aplurality of parallel elongated passageways in which each of theelongated passageways has a longitudinal axis perpendicular to the widthof the sheet. The extruded thermoplastic sheet is cut across its widthto form a plurality of separate plates, each having a preselectedlength. The separate plates are assembled one on top of another to forma stack of plates in which the elongated passageways in each plate arearranged in a common parallel direction perpendicular to the width ofthe stack. The stack has a width substantially equal to the width of theplates, a depth substantially equal to the preselected length of theplates, and a height determined by the number of plates assembled in thestack. The stack of assembled plates is then cut in a directiontransverse to the longitudinal axes of the elongated passageways at aplurality of preselected spaced-apart distances along the axes. Thecutting of the stack in this manner forms a plurality of separatestructures, each having a width and height substantially equal to thewidth and height of the stack and a thickness determined by thepreselected distance between the transverse cuts through the stack. Themethod further includes simultaneously fusing adjacently disposed platesto each other at at least one of the respective cut ends of the plates,simultaneously with cutting of the stack.

Other features of the method for forming a structure in accordance withthe method immediately set forth above includes the elongatedpassageways having a selected one of a number of cross sections,including the cross-sectional shapes enumerated above. Furthermore, theelongated passageways may be at least partially formed by a base wallhaving a first side defined by a surface extending across the width ofthe thermoplastic sheet, and a plurality of spaced-apart parallel wallsextending from a second side of the base wall in a direction normal tothe base wall. Also, the elongated passageways may be defined by aplurality of adjacently disposed U-shaped channels wherein the bottomsof the U-shaped channels define a surface extending across the width ofthe thermoplastic sheet. In yet another arrangement, the surfaceextending across the width of the thermoplastic sheet may be defined byone side of a serpentine wall, and the elongated passageways defined byalternating convex and concave curved portions on respective sides ofthe serpentine wall. Other features of the method of forming astructure, as set forth above, include the step of simultaneously fusingadjacently disposed plates to each other by heating at least one of thecut ends of each of the plates to a temperature sufficient to at leastpartially melt the respective cut ends whereupon, on cooling, the cutends are mutually fused together.

Other features of assembling of the plates includes the stacking of theplates in a structure having openings provided therein that are adaptedto provide access to the stack of plates for the purpose of wrapping atleast one band of a heat-shrinkable plastic material around the stack.Still other features of the method include cutting the stack ofassembled plates by making a plurality of simultaneous cuts atspaced-apart distances in a direction along the longitudinal axes of thepassageways of the plates.

In yet another aspect of the present invention, a method of forming astructure suitable for use as a core member includes extruding athermoplastic material into an elongated tubular shape, cutting theelongated tubular shape into a plurality of separate segments andaligning the separate segments in side-by-side relationship along theirpreselected lengths. The plurality of aligned separate segments is thenshrink-wrapped, with the shrink wrapping surrounding the alignedseparate segment and forming a bundle of shrink-wrapped segments. Theshrink-wrap bundle is then cut in a direction transverse to thelongitudinal axes of the segments, thereby forming a plurality ofseparate shrink-wrapped structures, each of having a thicknessdetermined by the preselected distances between the transverse cuts. Atleast one of the cut ends of the respective segments is simultaneouslyfused with an adjacently disposed aligned segment in the bundle duringthe cutting operation. Other features of the immediately above-describedmethod of forming a structure include the elongated tubes having a crosssection such as those previously described.

In still another aspect of the present invention, a method of forming astructure suitable for use as a core member includes extruding athermoplastic material into an elongated tubular shape, cutting theelongated tubular shape into a plurality of separate segments, andaligning a plurality of separate segments in side-by-side relationshipalong their lengths. The aligned separate segments are then depositedinto a consumable container formed of a material that is capable ofbeing cut by a thermal apparatus. The consumable container and thealigned segments deposited within the container are cut in a directiontransverse to the longitudinal axes of the aligned segments at aplurality of preselected spaced-apart distances along the longitudinalaxes of the segments. This forms a plurality of separate cores, eachhaving a thickness determined by the preselected distance along thetransverse cuts. Simultaneously with cutting through the depositedseparate segments and the consumable container, adjacently disposedaligned segments are simultaneously fused to each other at at least oneof the cut ends of the respective segments.

Other features of the method of forming a structure, in accordance withthe immediately above description, includes the consumable containerbeing formed of expanded polystyrene. Additional features include theconsumable container being disposed within a structure having openingsprovided therein that are adapted to provide access to the containercontaining the plurality of segments for the purpose of wrapping atleast one band of a plastic material around the consumable container.

Still other methods include cutting of the deposited separate segmentsand the consumable container by making a plurality of simultaneous cuts,desirably by heated wires, at spaced-apart distances along thelongitudinal axes of the segments.

In accordance with another aspect of the present invention, a membersuitable for use as a core has a pair of spaced-apart surfaces definingthe thickness of the member. The member also has a plurality ofadjacently disposed rows of a thermoplastic sheet structure, with therows being disposed in a direction parallel with the thickness of themember. Each row of the thermoplastic sheet structures have a definedwidth, at least one surface extending across the width, and a pluralityof elongated passageways disposed in parallel relationship with theaforementioned surface and with each other. Each of the elongatedpassageways have a longitudinal axis oriented perpendicular to thedirection of the width of the sheet. A portion of the at least onesurface is fused with a portion of the at least one surface of anadjacently disposed row of the thermoplastic sheet structures.

Other features of the member suitable for use as a core include thefused portions of the respective surfaces being positioned at at leastone of the pair of spaced-apart surfaces defining the thickness of themember. Also, the elongated passageways may have any of a number ofhollow cross sections, including rectangular, triangular, circular,hexagonal, or may have at least one transversely disposed internal wallwhich forms a plurality of separate elongated hollow cells extendingalong the length of each of the passageways.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the structure and operation of thepresent invention may be had by reference to the following detaileddescription when taken in conjunction with accompanying drawings:

FIG. 1 is a three-dimensional view of a structure suitable for use as acore member, made in accordance with the method embodying the presentinvention;

FIG. 2 is a three-dimensional view of an elongated tubular shape havinga hollow circular cross-section;

FIG. 3 is a three-dimensional view of an elongated tubular shape havinga hollow triangular cross-section;

FIG. 4 is a three-dimensional view of an elongated tubular shape havinga hollow square cross-section;

FIG. 5 is a three-dimensional view of an elongated tubular shape havinga hollow hexagonal cross-section;

FIG. 6 is a three-dimensional view of an elongated tubular shape havinga plurality of transversely disposed internal walls which form aplurality of separate elongated hollow cells extending along the lengthof the elongated tubular member;

FIG. 7 is a schematic diagram showing the operational flow of a firstembodiment of the method, in accordance with the present invention, offorming a structure suitable for use as a core member;

FIG. 8 is a three-dimensional view of a thermoplastic sheet structureused in one embodiment of the method of forming a structure suitable foruse as a core member, in accordance with the present invention;

FIG. 9 is a three-dimensional view of another arrangement of a sheetstructure suitable for use in carrying out the method embodying thepresent invention;

FIG. 10 is a three-dimensional view of another embodiment of athermoplastic sheet structure suitable for use in a method of forming astructure in accordance the present invention;

FIG. 11 is a three-dimensional view of yet another thermoplastic sheetstructure suitable for use in a method of forming a structure, inaccordance with the present invention;

FIG. 12 is a schematic diagram of another embodiment of the method offorming a structure suitable for use as a core member, in accordancewith the present invention;

FIG. 13 is three-dimensional view of an alternative embodiment of themethod embodying the present invention, in which elongated segments arealigned within a consumable box;

FIG. 14 is a three-dimensional view of a structure for holding aplurality of cut segments in the course of carrying out an embodiment ofthe method of forming a structure suitable for use as a core member inaccordance with the present invention;

FIG. 15 is a three-dimensional view of a heat-shrink wrapped bundle oftubes in accordance with one aspect of the method of forming a structureembodying the present invention;

FIG. 16 is a side view of a structure suitable for use as a core member,formed in accordance with the method of the present invention in whichheat-shrinkable plastic film encases the bundle as shown in FIG. 15; and

FIG. 17 is a plan view of a structure, embodying the present invention,that is suitable for use as a core member.

DETAILED DESCRIPTION OF PRESENTLY PREFERRED EXEMPLARY EMBODIMENTS

The present invention is described by reference to various embodimentsof a method for forming a structure 10, as shown in FIG. 1, suitable foruse as a core member, e.g., such as the cores used in multi-ply panels,various laminated panel constructions, or as stand-alone structuralmembers. Such cores and panels are used in many fields, such astransportation, housing, marine, architectural, and other fields. Thestructure 10 is typically used as a core on which a planar panel isapplied to one, or usually, both sides of the structure 10. The planarpanels may be plywood, aluminum or other metal, plastic, fiberglass,fabric such as found in wall coverings, and carpeting, or othermaterial.

As shown in FIGS. 2-6, in one arrangement of the structure 10, shortsections of an elongated tubular shape are arranged normal to the broadsurfaces of the panel and, due to their short columnar length,advantageously exhibit high strength along the longitudinal axes of theshort columns. Although a circular shape 12, as shown in FIG. 2, is usedin the following description of the preferred exemplary embodiments ofthe method for forming a structure 10, other shapes such as a tubularmember 14 having a hollow triangular cross section as shown in FIG. 3, atubular member 16 having a hollow square cross section, as shown in FIG.4, a tubular member 18 having a hexagonal cross section, as shown inFIG. 5, or a tubular member 20 having one or more transversely disposedinternal walls which form a plurality of separate elongated hollow cellsextending along the length of the tubular member 20, as shown in FIG. 6.Moreover, the tubular member may have a non-uniform cross section, i.e.,the cross-sectional area may vary along its length to form taperedsegments. In carrying out the method embodying the present invention, itis particularly desirable that the elongated tubular members be formedof a thermoplastic material such as polyethylene, polypropylene,polyvinyl chloride, or other thermoplastic material suitable for highforming rate extrusion processing.

In a first exemplary preferred embodiment of a method, in accordancewith the present invention, of forming a structure 10, a thermoplasticmaterial is discharged from an extruder 22 as an elongated tubular shape24 as shown schematically in FIG. 7. The tubular shape 24 is illustratedand used herein in a generic sense and may encompass any one or moretubular shapes such as the aforementioned cross sections, or othervariations and alterations of such cross sections. In shapes havinghollow cross sections, it is highly desirable to extrude thethermoplastic material as a solid rod 26 and then shape the exteriorwall of the tubular shape 24 by expanding the solid rod 26 in a vacuumsizer 28 which simultaneously forms a hollow void in the center of theextruded shape 24. The extruded shape 24, either with or without vacuumsizing is allowed to cool, or actively cooled, to a temperature at whichit is self supporting and can be readily cut into separate segments 30,each having a preselected length and a longitudinal axis 32 extendedalong the preselected length of the segments 30. The cutting operationmay advantageously be accomplished by a rotating blade which rotates ata speed coordinated with the extrusion rate of the tubular member 24 sothat each segment 22 has substantially the same length, end-to-end.

The cut segments 30 are then aligned in side-by-side relationship alongtheir preselected lengths. As shown in the schematic diagram of FIG. 7,the cut segments 30 are aligned while moving along an inclined guideway34 in which sides of the guideway converge toward a spaced-apartdistance that is substantially equal to the preselected length of thesegments 30. Therefore, the segments 30 are self-aligned as they passdown the inclined guideway 34. As an aid to movement of the segments 30,the guideway 34 may have a vibrated surface which agitates the segments30 to aid in the movement and alignment of the segments 30.Alternatively, the guideway 34 may use means other than gravity to thesegments 30 toward the right, as viewed in FIG. 7, such as by a movingbelt 36, or an air assist.

A preselected number of the aligned segments 30 are then formed into arow 40 having a preselected width, determined by the number of alignedsegments 30 that are in abutting contact with each other along the widthof the row 40. The rows 40 of aligned segments may be formed by fusingat least one of the cut ends of each of the aligned segments with anadjacently disposed one of the segments 30. The fusing of the cut endsmay be accomplished by heating the ends to a temperature sufficient toat least partially melt the cut ends of the aligned segments 30 to atemperature sufficient to at least partially melt the ends. This can beaccomplished by a heated wire, by a heated plate 38 as shown in FIG. 7,or by other heat sources such as a laser or ultrasound. Alternatively,the cut ends of the aligned segments 30 may be mechanically bondedtogether by passing an abrasive surface or mechanical cutting toolacross the ends of the segments 30 which make up one row 40 of thesegments 30. The rows 40 of the aligned segments 30 are then assembled,one on top of another, to form a stack 42 of rows 40. Alternatively, thestack 42 may have the rows 40 aligned vertically in abuttingrelationship with one another. As illustrated in FIG. 7, the stack 42has a width w substantially equal to the width of the rows 40, a depthsubstantially equal to the preselected length l of the segments 30 and aheight h determined by the number of rows 40 of aligned segmentsassembled in the stack 42.

The stack 42 of assembled rows 40 of segments 30 (shown rotated 90degrees for clarity) is then cut along lines that lie in a directiontransverse to the longitudinal axis 32 of the aligned segments 30 at aplurality of spaced-apart distances along the longitudinal axes 32.Advantageously, the cutting may be accomplished by a plurality of heatedwires 44 that, as also described below, simultaneously fuses the cutends of the segments 30. The spaced-apart distances of the cuts willdetermine the final thickness of the structure 10. For example, if theassembled stack 42 has a width of forty-eight inches, a length offorty-eight inches, and a height of forty-eight inches, and it isdesired that the resultant structures 10 have a thickness of one inch,the heated wires 44 would be spaced one inch apart. Thus, a 4.0 ft.×4.0ft.×4.0 ft. stack 42 will yield forty-eight one-inch thick structures 10having a 4.0 ft.×4.0 ft. height and width.

Alternatively, instead of using hot wires 44, other thermal cuttingmethods may be used, such as laser, a heated blade, a saw blade which isable to provide sufficient heat to both cut and fuse the cut ends of thesegments 30, or other methods.

If desired, the rows 40 of assembled segments 30 may be assembled into astack 42 by placing the rows 40 into a consumable container 46 formed ofa material that is capable of being kept by a thermal apparatus, such asthe aforementioned heated wire. Desirably, the consumable container 46is formed of an expanded or foamed plastic material that is readily cutby a heat source, such as expanded polystyrene. Other materials suitablefor construction of the consumable container 46 include reprocessedscrap tubes, cardboard, and polyethylene.

In making the final transverse cuts of the stacked rows 40, it may bedesirable to simultaneously cut the outer ends of each of the elongatedsegments 30 to assure that the outer structures 10 have a uniformthickness. This could also compensate for any misalignment of thesegments 30 which may result in an uneven surface on the outermoststructures 10. Also, as described below in greater detail, theconsumable container 46, if desired, may be wrapped in a heat-shrinkableplastic material prior to cutting the stack of assembled rows.

When using a thermal apparatus, such as the aforementioned hot wire 44or other apparatus, the heat produced by the thermal apparatus should besuch that it not only cuts i.e., severs, the segments 30 containedwithin the stack 42, but also provides sufficient heat to at leastpartially melt the cut ends of the segments 30 and fuse the ends ofadjacent cut segments to each other. If it is desired to later use thestructure 10 in a panel assembly that has curved surfaces, or for otheruses in which a curved core is desired, one surface of the structure 10should be fused and the opposite surface of the structure 10 not fused,i.e., the open ends of the segments 30 not joined together. This can beeasily accomplished using the method embodying the present invention.For example, during the cutting operation illustrated at the right endof the schematic diagram of FIG. 7, the temperature of the hot wires 44can be controlled so that one set of wires has a temperature sufficientto cut and fuse the cut ends of the segments 30, whereas an alternatingset of the hot wires 44 has a temperature sufficient to only cut thesegments 30 without fusing the cut ends. For example, the first hot wire44, positioned at the left end of the stack 42, may be controlled tohave a temperature sufficient to not only cut the ends of the segments30, but also to fuse the cut ends, whereas the second wire 44 from theleft end may be controlled to a temperature sufficient to only cut thesegments 30. In like manner, the third wire 44 from the left end may becontrolled to a temperature sufficient to cut and fuse the segments 30.Thus, the two left-hand structures 10 severed from the stack 42 eachhave one surface at which the cut segments are fused and an oppositesurface at which the cut segments are not fused together. This permitsthe structure 10 to be bent in a shape where the uncut surface can becurved into a convex curve, with the corresponding fused surface curvedinto a concave curved surface shape.

In a second preferred embodiment forming a structure 10, according tothe present invention, suitable for use as a core member, a continuousthermoplastic sheet 48, having a predefined width w, is used in theinitial step of the method as illustrated in FIG. 12. The thermoplasticsheet 48 desirably has a plurality of elongated passageways 52 that aredisposed in parallel relationship with at least one surface of the sheetand with each other. Each of the elongated passageways 52 have alongitudinal axis 54 that is disposed perpendicular to the direction ofthe width W of the sheet 48.

Alternate forms of the thermoplastic sheet 48 are shown in FIGS. 8-11.In FIG. 8, the longitudinal passageways 52 have a hollow rectangularcross-section. Other shapes of hollow cross sections may be formedbetween the pair of planar surfaces of the sheet 48 and include hollowcircular cross sections, hollow triangular cross sections, hollowhexagonal cross sections, and other arrangements as described above withrespect to the elongated tubular extruded shapes 24. In the structureshown in FIG. 9, the elongated passageways 56 are at least partiallyformed by a base wall 58 having a first side 60 which defines thesurface extending across the width of the thermoplastic sheet, and byplurality of spaced-apart parallel walls 62 that extend from a secondside of the base wall 58 in a direction normal to the base wall 58. Theupper portion of the passageways 56 are closed when a second sheet isassembled on top of the first sheet, thereby completing the enclosurearound the passageway 56. Another arrangement of the thermoplasticsheet, illustrated in FIG. 10, has the form of a series of adjacentlydisposed U-shaped channels 64 wherein the bottom of the U-shapedchannels 64 define a surface 66 extending across the width of the sheet.In FIG. 11, the thermoplastic sheet is defined by one side 68 of aserpentine wall 70 and elongated passageways 72 are defined byalternating convex and concave curved portions on respective sides ofthe serpentine wall 70. The serpentine wall 70 extends across the widthof the thermoplastic sheet.

After being expelled from the extruder 22, a thermoplastic sheet such asthe sheet 48 shown in FIG. 8, is either passively or actively cooled andcut transversely across the width of the sheet 48 to form a plurality ofseparate plates 74, as shown schematically in FIG. 12. The plates 74each have a preselected length l extending in a direction parallel tothe longitudinal axes 54 of the passageways 52. The separated plates 74are then assembled one on top of another to form a stack 76 having awidth substantially equal to the width of the plates 74, a depth dsubstantially equal to the preselected length l of the plates 74, and aheight h determined by the number of plates 74 assembled in the stack76. The stack 76 of assembled plates 74 are then simultaneously cut at aplurality of locations, in a direction transverse to the longitudinalaxes 54 of the elongated passageways 52. The multiple cutting operationdivides the stack 76 into a plurality of separate structures 84, asillustrated in plan view in FIG. 17. Each of the structures 84 have awidth and height substantially equal to the width and height of thestack 76, and a thickness determined by the preselected distance betweenthe transverse cuts through the stack 76. As described above, desirablythe stack 76 is simultaneously cut by a plurality of hot wires 44 drawnthrough the stack 76 whereat the spacing between the wires 44 determinesthe thickness of the severed structure 84. Also, as described above, thecut ends of the plates 74 are desirably fused together at at least onesurface of the structure 84. The temperature of the hot wires 44 drawnthrough the stack 76 will determine whether the plates 74, at thattransverse location, are merely cut or cut and simultaneously fused toadjoining plates 74.

Prior to cutting the assembled plates 74, the plates 74 may be stackedin a holder, or structure 78, as illustrated in FIG. 14, that has sideopenings and a bottom clearance provided therein which provide access toa stack 76 of plates 50 assembled within the holder 78, for wrapping atleast one band of a plastic material around the stack 76. Preferably,the plastic material is a heat-shrinkable film. Heat-shrink wrapping isgenerally defined as a plastic film having preformed strains in whichthe strains are released by raising the temperature of the film, causingthe film to shrink-fit around an object about which it is wrapped, i.e.,the stack 76.

Thus, it can be seen that the above method provides a structure, ormember, 84 as illustrated in FIG. 17, suitable for use as a core havinga plurality of adjacently disposed rows 40 of thermoplastic plates 74 inwhich the passageways 52 in the rows 40 are disposed in a directionnormal to the thickness of the member 84. Each of the thermoplasticplates 74 have a predefined width, at least one surface extending acrossthe width of the plate 74, and a plurality of elongated passageways 52disposed in parallel relationship with at least one surface 60 of themember 84 and with each other. Also, each of the elongated passageways52 have a longitudinal axis 54 that is perpendicular to the direction ofthe width of the plate 74. Importantly, a portion of at least one end ofeach row 40 adjacent the broad surface of the member 84 is fused with aportion of an adjacently disposed row 40 of the thermoplastic plates 74.It can also be readily seen that the member 84 may have any of thecross-sectional shapes described above with respect to the tubularshapes 24 and the thermoplastic sheets 48.

In a third embodiment of the method, embodying the present invention, offorming a structure 10 suitable for use as a core member, separatesegments 30 are provided as described above, by extruding athermoplastic material into an elongated tubular shape 24, cutting theelongated tubular shape 24 into a plurality of separate segments 30which have a preselected length and a longitudinal axis 32, and aligningthe separate segments 30 in side-to-side relationship along theirpreselected lengths as shown in FIG. 15. The elongated tubular shape 24may have any of the above-described cross-sectional shapes, and as anaid to aligning the separate segments 30, the segments 30 may be movedalong a guideway 34 as described above, which has side walls thatconverge to a spaced-apart distance substantially equal to the length ofthe segments 30. If desired, either the guideway 34 or the segments 30may be agitated during movement to assure that the segments 30 arealigned in abutting relationship with each other along their lengths.

The aligned separate segments 30 are then shrink-wrapped by aheat-shrinkable film 80 whereby a consolidated bundle of shrink-wrappedsegments 30 is provided. The bundle may then be simultaneously cut at aplurality of spaced-apart locations, in a direction transverse to thelongitudinal axes 32 of the segments 30 as described above. Thus, aplurality of separate shrink-wrapped structures 10 which have a film 80of the shrink wrapping around the exterior periphery of the structure 10as illustrated in FIG. 16. It has been found that the shrink-wrappingfilm 80 can be readily cut by the thermal devices, such as the hot wires44 used to cut and/or fuse the thermoplastic segments 30 or plates 50.

In a fourth preferred embodiment of the method of forming a structure10, in accordance with the present invention, that is suitable for useas a core member, a thermoplastic material is extruded into an elongatedtubular shape 24 as described above. Also, as described above, theelongated tubular shapes 24 are then cut into a plurality of separatesegments 30, each having a preselected length l and a longitudinal axis32. The separate segments 30 are then aligned in side-by-siderelationship along their respective lengths, as described above, anddeposited into a consumable container 82, as illustrated in FIG. 13. Theconsumable container is desirably formed of expanded polystyrene orother material that can be readily cut by thermal apparatus, such as ahot wire 44.

After being deposited in the consumable container 82, as shown in FIG.13, the separate segments 30 and container 82 can be simultaneously cutin a direction transverse to the longitudinal axes of the alignedsegments 30 at a plurality of preselected spaced-apart distances in adirection along the longitudinal axes 32 of the segments 30. Thisoperation, as described at various points above, forms a plurality ofseparate structures 10 each having a thickness determined by thepreselected distance between the transverse cuts. Simultaneously,depending upon the temperature of the thermal device, selected cut endsof the segments may be fused with an adjacently disposed cut end at atleast one other segment 30. In this method, the elongated tubes 24 mayhave any of the cross-sectional shapes defined above although, for easeof the description in the schematic diagrams, a circular cross sectionhas been used for illustrative purposes in the drawings. Also, themethod described immediately above may include agitating the segments 30along a guideway 34, as shown in FIG. 7, during moving the segments 30along the guideway 34 for the purpose of aligning the ends of thesegments 30 and positioning the segments 30 in abutting side-by-siderelationship.

Thus, it can be seen that by the methods described above, that astructure 10, or plate 84, can be easily formed in an economical manner.The methods described herein do not require adhesive joining or the useof a gutter or trough-like fixture to hold an aligned bundle of tubularsegments as they are cut, a single pass at a time. Forming only a singlestructure at a time is time consuming and labor intensive. Moreover,increased handling of the segments during multiple single step cuttingoperations can lead to misalignment of the segments between successivecuts.

Although the present invention is described in terms of preferredexemplary embodiments, with specific illustrative shapes of tubularmembers and thermoplastic sheet structures and suitable thermoplasticmaterials, those skilled in the art will recognize that changes in thoseshapes, arrangements and materials may be made without departing fromthe spirit of the invention. Such changes are intended to fall withinthe scope of the following claims. Other aspects, features, andadvantages of the present invention may be obtained from a study of thisdisclosure and the drawings, along with the appended claims.

What we claim is:
 1. A method of forming a structure suitable for use asa core member, comprising: forming a row of aligned segments having anelongated tubular shape, each of said segments having a thermoplasticcomposition, a pair of spaced apart ends defining the length of saidsegments, and a longitudinal axis extending along said length, saidaligned segments being in substantially abutting contact along theirrespective lengths and said row having a preselected width; assemblingsaid rows of the aligned segments in abutting relationship with anotherone of said rows to form a stack of said rows of aligned segments, saidstack having a width substantially equal to the width of said rows ofaligned segments, a depth substantially equal to the preselected lengthof said segments, and a height determined by one of the number of rowsof aligned segments assembled in said stack and the preselected width ofsaid rows, and simultaneously cutting said stack of assembled rows ofaligned segments in a direction transverse to the longitudinal axes ofthe aligned segments at a plurality of preselected spaced apartdistances in a direction along said longitudinal axes and forming aplurality of separate structures each having a width and heightsubstantially equal to the width and height of said stack and athickness determined by the preselected distance between said transversecuts, and simultaneously fusing adjacently disposed aligned segments toeach other at at least one of the respective cut ends of the segments.2. A method of forming a structure, as set forth in claim 1, whereinsaid segments having an elongated tubular shape are formed by extrudinga thermoplastic material into a tubular shape having a continuous lengthand subsequently cutting said extruded tubular shape into said segmentshaving an elongated tubular shape.
 3. A method of forming a structure,as set forth in claim 1, wherein said forming a row of aligned segmentshaving an elongated tubular shape, includes forming a row of elongatedtubes having a hollow circular cross section.
 4. A method of forming astructure, as set forth in claim 1, wherein said forming a row ofaligned segments having an elongated tubular shape, includes forming arow of elongated tubes having a hollow rectangular cross section.
 5. Amethod of forming a structure, as set forth in claim 1, wherein saidforming a row of aligned segments having an elongated tubular shape,includes forming a row of elongated tubes having a hollow triangularcross section.
 6. A method of forming a structure, as set forth in claim1, wherein said forming a row of aligned segments having an elongatedtubular shape, includes forming a row of elongated tubes having a hollowhexagonal cross section.
 7. A method of forming a structure, as setforth in claim 1, wherein said forming a row of aligned segments havingan elongated tubular shape, includes forming a row of elongated tubeshaving at least one transversely disposed internal wall forming aplurality of separate elongated hollow cells extending along the lengthof said tube.
 8. A method of forming a structure, as set forth in claim1, wherein said aligning a plurality of separate segments inside-by-side relationship includes moving said segments along a guidewayhaving side walls that converge to a spaced apart distance substantiallyequal to the length of said segments.
 9. A method of forming astructure, as set forth in claim 8, wherein said method includesagitating at least one of said segments and said guideway during movingsaid segments along said guideway.
 10. A method of forming a structure,as set forth in claim 1, wherein said forming a row of said plurality ofaligned segments includes fusing at least one of the cut ends of each ofsaid aligned segments to the cut end of at least one adjacently disposedsegment.
 11. A method of forming a structure, as set forth in claim 10,wherein said fusing the cut ends of said aligned segments includesheating said ends to a temperature sufficient to at least partially meltthe cut ends of said aligned segments.
 12. A method of forming astructure, as set forth in claim 1, wherein said forming a row of saidplurality of aligned segments includes mechanically bonding at least oneof the cut ends of each of said aligned segments to the cut end of atleast one adjacently disposed segment.
 13. A method of forming astructure, as set forth in claim 1, wherein said assembling said rows ofaligned segments one on top of another includes depositing said rowsinto a consumable container formed of a material that is capable ofbeing cut by a thermal apparatus.
 14. A method of forming a structure,as set forth in claim 13, wherein the cutting step includes cuttingthrough the consumable container with the thermal apparatus and saidthermal apparatus is a heated wire.
 15. A method of forming a structure,as set forth in claim 14, wherein said consumable container is formed ofexpanded polystyrene.
 16. A method of forming a structure, as set forthin claim 13, wherein said consumable container is disposed within astructure having openings provided therein that are adapted to provideaccess to said stack of the rows of aligned segments for wrapping atleast one band of a plastic material around said stack.
 17. A method offorming a structure, as set forth in claim 16, wherein said plasticmaterial is a film having preformed strains in which the strains arereleased by raising the temperature of the film, causing the film toshrink-fit around said stack.
 18. A method of forming a structure, asset forth in claim 1, wherein said assembling said rows of alignedsegments one on top of another includes wrapping said stack of said rowsof aligned segments with shrink wrapping prior to cutting said stack.19. A method of forming a structure, as set forth in claim 1, whereinsaid cutting said stack of assembled rows of aligned segments includesmaking a plurality of simultaneous cuts at said spaced apart distancesin said direction along the longitudinal axes of the segments.
 20. Amethod of forming a structure, as set forth in claim 19, wherein saidsimultaneous cuts are made by simultaneously passing a plurality ofheated wires through said stack.
 21. A method of forming a structuresuitable for use as a core member, comprising: selecting a plurality ofseparate segments formed of a thermoplastic material, each of saidseparate segments being formed of a thermoplastic material and having apreselected length and a longitudinal axis extending along saidpreselected length; aligning a plurality of said separate segments inside-by-side relationship along their preselected lengths; depositingsaid aligned plurality of said separate segments into a consumablecontainer formed of a material that is capable of being cut by a thermalapparatus; cutting through said deposited separate segments and saidconsumable container in a direction transverse to the longitudinal axesof the aligned segments at a plurality of preselected spaced apartdistances in a direction along said longitudinal axes and forming aplurality of separate structures each having a thickness determined bythe preselected distance between said transverse cuts, andsimultaneously fusing adjacently disposed aligned segments to each otherat least one of the cut ends of the respective segments.
 22. A method offorming a structure, as set forth in claim 21, wherein prior to saidselecting a plurality of separate segments, said method includesextruding a thermoplastic material into an elongated tubular shapehaving a continuous length and cutting said elongated tubular shape intoa plurality of separate segments each having a preselected length.
 23. Amethod of forming a structure as set forth in claim 22, wherein saidextruding a thermoplastic material into an elongated tubular shapeincludes extruding an elongated tubular shape having a hollow circularcross section.
 24. A method of forming a structure, as set forth inclaim 22, wherein said extruding a thermoplastic material into anelongated tubular shape includes extruding an elongated tubular shapehaving a hollow rectangular cross section.
 25. A method of forming astructure, as set forth in claim 22, wherein said extruding athermoplastic material into and elongated tubular shape includesextruding an elongated tubular shape having a hollow triangular crosssection.
 26. A method of forming a structure, as set forth in claim 22,wherein said extruding a thermoplastic material into an elongatedtubular shape includes extruding an elongated tubular shape having ahollow hexagonal cross section.
 27. A method of forming a structure, asset forth in claim 22, wherein said extruding a thermoplastic materialinto an elongated tubular shape includes extruding an elongated tubularshape having at least one transversely disposed internal wall forming aplurality of separate elongated hollow cells extending along the lengthof said tubular shape.
 28. A method of forming a structure, as set forthin claim 21, wherein said aligning a plurality of separate segments inside-by-side relationship includes moving said segments along a guidewayhaving side walls that converge to a spaced apart distance substantiallyequal to the length of said segments.
 29. A method of forming astructure, as set forth in claim 21, wherein said method includesagitating said guideway during moving said segments along said guideway.30. A method of forming a structure, as set forth in claim 21, whereinsaid fusing the cut ends of said aligned segments includes heating saidends to a temperature sufficient to at least partially melt the cut endsof said aligned segments.
 31. A method of forming a structure, as setforth in claim 21, wherein said consumable container is formed ofexpanded polystyrene.
 32. A method of forming a structure, as set forthin claim 21, wherein said consumable container is disposed within astructure having openings provided therein that are adapted to provideaccess to said consumable container containing said plurality ofsegments for wrapping at least one band of a plastic material aroundsaid consumable container.
 33. A method of forming a structure, as setforth in claim 21, wherein said cutting said deposited separate segmentsand said consumable container includes making a plurality ofsimultaneous cuts at said spaced apart distances in said direction alongthe longitudinal axes of the segments.
 34. A method of forming astructure, as set forth in claim 33, wherein said simultaneous cuts aremade by simultaneously passing a plurality of heated wires through saiddeposited separate segments and said consumable container.